The present invention relates to the application of scanning control signals to television receivers and, more particularly, to a method and apparatus for applying a scanning control signal to a television receiver which isolates the receiver electrically from the equipment or device generating such signal.
Standard home television receivers are increasingly being used to display information visually which is not broadcast over air waves. The device which generates the desired information to be displayed typically is connected to the antenna input of the TV receiver and provides a scanning control signal, e.g., a full composite video signal, through such input to direct the receiver to produce the desired display. The video game arrangements which have proliferated in the last several years are examples of devices which utilize television receiver displays. The scanning control signal of such a game arrangement typically directs the receiver to produce a game background and moving players, paddles and/or other objects.
Television receivers are designed to receive information defining a desired screen display on a radio frequency carrier signal. The auxiliary devices which are connected to the antenna input therefore also include most often a radio frequency oscillator, as well as the circuitry and other equipment necessary to generate the desired control signal. Because of such, there has been concern that the auxiliary equipment connected to the antenna input may inadvertently radiate radio frequency or other interfering radiation. While care is taken to design the auxiliary equipment so as not to cause unwanted radiation during normal operation, it is very difficult to eliminate them. This is especially true in equipment having long conductors carrying RF signals.
Because of this potential radiation hazard, all devices designed to be connected to a television receiver antenna input must be type-approved for such use by the U.S. Government before they can be marketed. This has delayed introduction to the market of many devices which, in fact, can be safely connected to television receivers. This problem is aggravated by the escalating number of different proposed devices designed to utilize television sets as display terminals.